This invention relates generally to support structures, and more particularly to systems for supporting the body weight of a person to facilitate various recreational and/or vocational activities.
Various types of braces attachable to a wearer's leg are disclosed in the prior art. In connection with snow skiing applications, U.S. Pat. No. 3,928,872 (Johnson) discloses a pair of devices, each of which is securable to a leg of the skier to provide flexural knee and leg support. In each device a spring is employed to interconnect an upper support sleeve positioned about the skier's leg above the knee to a lower support sleeve positioned below the knee, and the stated objectives of the devices are to reduce weight load on the knees, absorb shock and reduce the strain when the knee flexes. The use of resilient spring means, as employed in the devices disclosed in the Johnson patent, appears to inherently produce an oscillatory or bouncing effect on the skier's body as the angle of his or her knee flexure changes during a ski run owing to the uneven terrain of a typical ski slope. The more rigid the spring, the more pronounced the rebounding effect will be, which effect is quite undesirable for controlled skiing. Moreover, the frequency of spring movement in the Johnson devices will likely rarely match the frequency of flexure of the knee as caused by the traversal of a skier over the terrain. Thus, the Johnson devices may tend to take the skier out of synchronism with the terrain, thereby further contributing to the loss of the skier's balance and control.
To obviate the deficiencies of the devices disclosed in the Johnson patent a body weight support system employing non-resilient flexure means was invented by Thomas P. Waddell, one of the joint inventors of the subject matter of the instant application, and is described in detail in copending application Ser. No. 411,404, filed on Aug. 25, 1982, and hereinafter referred to as the "Waddell application". The subject matter of the Waddell application is incorporated herein by reference.
In the support system disclosed in the Waddell application a brace is provided for securement to the legs of a person. The brace basically comprises a frame-like construction including an upper leg support section, a lower leg support section and flexure means between them. Securement means, such as conventional straps having buckles at one end thereof, are employed to attach the upper leg support section and the lower leg support section about the leg of the user. The upper leg support section extends along the thigh of the user and terminates at its upper end immediately adjacent the buttocks-thigh interface to form a seat. The lower leg support section is a tubular member of a generally U-shape having a pair of upwardly extending leg portions and an arcuate bottom portion. The leg portions extend upwardly along the lower leg and terminate adjacent the knee. The curved bottom portion of the lower leg support section is located adjacent the skier's boot, and is adapted to be attached thereto.
In the brace disclosed in the Waddell application the preferred non-resilient flexure means includes a pair of spaced-apart flexure assemblies. Each assembly is located adjacent the knee of the wearer and includes a plurality of disk-like cylindrical segments mounted for pivotal movement relative to each other. The disk-like segments of both assemblies are joined together by a common tensioning cable extending through aligned central passages in the segments. One end of the tensioning cable is connected to an adjustment means adapted to control the degree of slack in the cable, and thereby adjust and set the degree of flexure provided by the flexure assemblies. The opposite end of the tensioning cable is retained against movement in a frame member forming part of the upper leg support section.
In the support system disclosed in the Waddell application substantial resistance to further flexural movement of the knee is encountered once the flexure assemblies have moved through an annular range up to a predetermined angle set by the adjustment of the common tensioning cable. The slight, or residual resiliency exhibited by the flexure assemblies at the maximum flexure angle (i.e., when the tensioning cable is taut) is on the order of approximately 10% and results from the slight "give" inherent in the tensioning cable.
Although the system of the Waddell application overcomes the various problems enountered with resilient flexure means of the type disclosed in the Johnson patent, it may exhibit certain inherent undesirable characteristics during some uses. Specifically, as a skier is moving over the uneven terrain of a typical ski slope, his or her knee flexure will constantly be changing, and may actually reach the maximum flexure angle at several different times during the run. In the event that the skier's knees do reach the maximum flexure angle, the body may be "jolted" due to the substantial resistance to further flexural movement created by the tensioning cable once the maximum flexure angle of the flexure assemblies has been reached. The small, e.g., approximately 10%, resiliency inherent in the cable of the Waddell system does not relieve this jolting effect to the desired optional degree.
From the above discussion it should be apparent that the spring-type system disclosed in the Johnson patent can result in the loss of balance and control during a ski run due to excessive resiliency. While the use of the non-resilient flexure assemblies disclosed in the Waddell application overcomes the problems associated with the Johnson device, such assemblies may nevertheless cause undesired jolting of the skier's body.
U.S. Pat. No. 4,144,881 (Chappell) discloses an orthopedic prosthetic device which can be incorporated into a knee support. The device includes a plurality of interlocking links, in the form of crescent-shaped disks, that can be adjusted to permit a desired degree of motion in the plane of articulation. This device does not provide an upper body weight support system, and also has virtually no resiliency or ability to move once the knee reaches the adjusted degree of rotation of the links.